TNF and Cognitive impairment: Enzyme-linked immunosorbent assay (ELISA) was used to detect the expression level of serum TNF-α in each group, and the colorimetric method was adopted for detecting the expression level of serum iNOS in each group; Moreover, cognitive function of patients was assessed by MATRICS Consensus Cognitive Battery (MCCB), disease burden was assessed by Family Burden of Disease Scale (FBS), and the correlation between the expression of serum TNF-α and iNOS as well as cognitive impairment and disease burden was analyzed by Pearson method.